Each pair of definitions is for two words, where the second word is the first word with a letter deleted (example: brand & band). The length of the first word in each pair is provided, along with the position of the deleted letter to obtain the second word.

1) firmament (6 letters) & (delete 2nd letter) a port or harbor
2) a monster in fairy tales that eats humans (4 letters) & (delete 2nd letter) a natural substance from which metal can be extracted
3) a member of a royal family (6 letters) & (delete 4th letter) cost or charge
4) a marsh or bog (5 letters) & (delete 4th letter) to exchange